In attempts at making a vehicle body from fiber reinforced structural composite assemblies, prior art workers have employed hollow sections for the same reason that separate metal stampings are welded together to create a hollow section in conventional vehicle construction; namely, to increase the stiffness of a given component since stiffness increases by the cube of the increase in section thickness.
Hollow section fiber reinforced thermoset composites have been formed by gluing two panels together or molding the entire component around a foam core, blow molded inserts, and inflatable air bags in order achieve a desired stiffness level.
Hollow section fiber reinforced, thermoset composite assemblies have been proposed for use in the manufacture of a so-called space frame automobile structure wherein a reinforced structural composite side assembly or cage and reinforced structural composite floor module are bonded together by suitable adhesive and mounted on an underlying steel frame. The automobile space frame comprises opposing hollow, molded body side assemblies bonded together by suitable adhesive. Other reinforced composite components, such as a roof module and dash module, can also be incorporated in the structure.
Each hollow body side assembly includes glass reinforced, molded vinyl ester panels separated by a space or cavity therebetween. Each body side assembly is formed by positioning multiple glass fabric reinforcement preforms in a suitable mold, introducing thermosetting vinyl ester resin into the mold to impregnate the preforms, and heat curing the resin to form the hollow glass reinforced thermoset panel assembly.
Although fiber reinforced structural composites have been formed into hollow sections suitable for use in the construction of a vehicle body, such composites and process for making them into hollow sections have not resulted in a cost competitive alternative to the stamped/welded steel panel construction heretofore employed in motor vehicle construction.
There is thus a need for an improved method of making hollow section fiber reinforced structural composite assemblies for use as structural components in motor vehicle body and other constructions at lower cost. There is also a need for an improved method of making such hollow section fiber reinforced structural composite assemblies using other materials, such as thermoplastic materials, that will facilitate composite molding and bonding to form a simple or complex structural assembly and yet treatable to impart desirable thermoset properties to the final bonded assembly.
It is an object of the present invention to satisfy these needs.